The coatings so far in industrial use are the so-called solvent-borne coatings in which an organic solvent is used as a diluent solvent. Thus, the coatings contain a large amount of an organic solvent. However, in view of the recent concern about the environment, water-borne coatings in which the organic solvent content is reduced and water is used as a diluent solvent have been developed or under development.
Thus, in Japanese Kokai Publication Hei-07-53913, for instance, there is disclosed, as such a water-borne coating, a water-borne coating composition which comprises a resin obtained by at least partly neutralizing a polymer composed of an amide group-containing ethylenically unsaturated monomer, an acidic group-containing ethylenically unsaturated monomer and a hydroxyl group-containing ethylenically unsaturated monomer, and an aqueous dispersion of a carboxyl group-containing acrylic resin particles.
There is a problem, however, that compared with the earlier solvent-borne coatings, the coating film obtained from the so-far known water-borne coatings are generally poor in luster and coloration.
Accordingly, it is an object of the present invention to provide a water-borne base coating composition for automobiles which can give a coating film excellent in luster and in coloration.